1. Field of the Invention
The present invention relates to a method of tamping and stabilizing a track at a desired level, which comprises the steps of lifting the track to a temporary level, intermittently tamping the track and then advancing along the track in an operating direction, and stabilizing the tamped track at the desired level by imparting to the track horizontal vibrations extending in a direction perpendicular to the track, and applying to the vibrating track a vertical load to obtain the desired track level, as well as to a machine for carrying out this method.
2. Description of the Prior Art
A track tamping and stabilizing method and machine of this general type has been disclosed in U.S. Pat. No. 5,172,635. According to this patent, a track position correction obtained by tamping is combined with the subsequent compaction of the tamped track by imparting to the track horizontal vibrations extending in a direction perpendicular to the track and applying to the vibrating track a vertical load. The ballast supports for the track ties are obtained by immersing reciprocating tamping tools in the cribs between the ties and tamping the ballast under the ties whereby the homogeneity of the ballast bed is disturbed, and the tamped track is then lowered to the desired level. This dynamic stabilization of the tamped track avoids the initial settling of the track which is an unavoidable result of the tamping.
The dynamic track stabilization produces a controlled lowering of the track while a track stabilization car continuously advances along the track in an operating direction and the vertical load remains constant at a constant value. Immediately preceding the track stabilization in the operating direction and parallel thereto, a tamping machine advances continuously while a tamping assembly on the machine is displaced relative thereto to enable the ties to be intermittently tamped.
As has been known for some time and has been described, for example, in an article entitled "High-speed DTS `train tamps` track" in Railway Track & Structures, March 1984, pp. 48-52 (see particularly p. 48, col. 1, lines 39, 40, and col. 3, lines 7-9), in commercial practice the dynamic track stabilizers have worked continuously during the track surfacing operation while the machine advances continuously along the track. Such track surfacing has achieved world-wide success for more than a decade and, as mentioned on page 52, col. 2, of this article, particularly high production is obtained by combining the continuously advancing track high-speed stabilization machine with an equally continuous motion tamper.
U.S. Pat. Nos. 4,046,078, 4,046,079 and 4,430,946, and British patent No. 2,094,379 disclose intermittently advancing machine units combining track tamping with the dynamic stabilization of the tamped track. However, none of these machines combining track tamping with track stabilization in one operation have gained practical acceptance.